Taking the rails in Switzerland can get expensive very quickly. For a proper visit of at least a week, consider a Swiss Travel Pass, which includes trains, local public transport, and a number of attractions.
However, not all trains are covered by the pass. The Glacier Express between Zermatt and St. Mortiz, a popular sightseeing trip across the Swiss Alps, is one of them. The fare is free, but an additional seat reservation fee is required. You will be assigned a specific seat for the duration of the journey, with an option to add a meal as you will be on the train for much of the day.
If you don't mind changing trains, even with luggage, then you should consider taking the local trains instead, which travel on the same set of tracks so your views are exactly the same. These local trains are timed to connect to each other, so you won't have excessively long waits anywhere. They are also rarely full, so you will be away from the tourist crowds and can get to move around both sides of the train to enjoy the scenery. Some trains also have windows that can be drawn down so your camera won't need to battle an annoying glare.
My trip started bright and early in Zermatt. To search the schedules, input Zermatt to St. Moritz via Andermatt. The total journey time would be about 8 hours. This is a full day of sightseeing!
